Since a cellular communication system achieves reuse of limited spectrum resources, wireless communication technologies have been dramatically developed. In a cellular system, when there are services needing to be transmitted between two UEs (service data transmission from a UE 1 to a UE 2 for instance), service data is transmitted to a base station (evolved Node B (eNB)) 1 via an air interface, the eNB 1 transmits user data to an eNB 2 via a core network, and the eNB 2 transmits the service data to the UE 2 via an air interface. The service data transmission from the UE 2 to the UE 1 adopts a similar processing flow.
FIG. 1 is a diagram of cellular communication when UEs are located in an identical cell of an eNB according to the relevant art. As shown in FIG. 1, when the UE 1 and the UE 2 are located in an identical cell, although the eNB 1 and the eNB 2 are actually an identical site, two sets of radio spectrum resources will be still consumed in single data transmission.
Thus, it can be seen that if the UE 1 and the UE 2 are located in the identical cell and in proximity to each other, the above cellular communication method is not an optimal communication mode obviously. Actually, as mobile communication services are diversified, for example, as a social network, an electronic payment application and the like are more and more widely applied to a wireless communication system, the demand for service transmission between close users is increasing. Consequently, a D2D communication mode has been more and more widely concerned. D2D refers to direct transmission of the service data from a source UE to a target UE via an air interface without forwarding via the eNBs, and the communication mode is distinguished from a communication mode of a traditional cellular system. For users in near field communication, D2D saves the radio spectrum resources and reduces the data transmission burden of the core network. The D2D communication based on a cellular network is a novel technology for direct communications between multiple terminal devices supporting a D2D function under the control of a system, which can reduce the resource occupation of the system, increase the spectrum efficiency of the cellular communication system, reduce the transmitting power consumption of a terminal and reduce the network operation cost to a great extent.
In the D2D communication, the precondition of data transmission between the source UE and the target UE is the time frequency synchronization between a transmitter and a receiver firstly. That is, the source UE sends a D2D SS, and the target UE implements time frequency synchronization between the transmitter and the receiver according to the received D2D SS. A 3rd Generation Partnership Project (3GPP) has decided, on a ran1#74bis conference, that: the D2D SS contains a Zadoff-Chu (ZC) sequence, and the specific selection of the ZC sequence is to be determined by subsequent research. In a Long Term Evolution (LTE) system, a Sounding Reference Signal (SRS) for channel sounding and a Demodulation-Reference Signal (DM-RS) demodulated by a Physical Uplink Share Channel (PUSCH) are ZC sequences (or sequences obtained by performing cyclic shift expansion on the ZC sequences, sequences obtained by punching partial elements of the ZC sequences and the like). Without loss of generality, the source UE sends a D2D SS (ZC sequence) of which a length is N at a frequency domain position 1, and in this situation, there exist problems as follows needing to be solved.
1. An interference UE sends an SRS or a DM-RS of which the length is M at a frequency domain position 2 which is completely not overlapped with the frequency domain position 1 (time domain positions may be identical or different). Even if M is not equal to N, the SRS or DM-RS signal may be greatly correlated to the D2D SS. At this time, the target UE may take the DM-RS or the SRS of the UE 2 as the D2D SS by mistake so as to cause synchronization failure.
2. An interference UE (for example, a neighbour UE of the source UE) sends an SRS or a DM-RS of which the length is M at the frequency domain position 2 which is completely or partially overlapped with the frequency domain position 1 (the time domain positions may be identical or different). At this time, when the target UE performs time frequency synchronization between the transmitter and the receiver according to the received D2D SS, the SRS or the DM-RS sent by the interference UE may bring a great interference to the synchronization between the target UE and the source UE, the interference including that: (1) the accuracy of time frequency synchronization is reduced; and (2) the target UE may perform channel estimation by utilizing the received D2D SS, and the SRS or the DM-RS sent by the interference UE may bring a great negative influence on the accuracy of channel estimation.
Thus, it can be seen that in the method for sending a D2D SS in the relevant art, the DM-RS or the SRS sent by the interference UE easily brings interference to the D2D SS.
An effective solution is not currently available for the problem in the relevant art that the DM-RS or the SRS sent by the interference UE easily brings interference to the D2D SS.